1. Field of the Invention
The present invention relates to illumination apparatus, and, more particularly, to a multiple source lighting fixture having a multiple reflector optical system.
2. Description of the Prior Art
Prior approaches to improving surgical lighting have generally relied on increasing the size of the lighting fixture or the number of light sources. For example, Herold U.S. Pat. No. 3,927,313 discloses a surgical lighting fixture having several individual light sources evenly arranged around a central axis. A problem with conventional multiple source lightheads however, is that they produce multiple individual light beams which, in turn, produce multiple shadows when the beams are interrupted.
Single source lightheads eliminate the problem of multiple shadows but do not provide both high intensity and a large pattern of illumination. To achieve the desired intensity, the pattern of illumination must be limited or the wattage of the bulb increased. To achieve a large pattern, the intensity is reduced. Single source surgical lightheads generally offer their best characteristics at a pattern no greater than six inches and an intensity no greater than 6,000 foot candles.
In some applications, such as cardiovascular surgery, a larger area of illumination is desirable. In Europe, the trend is toward larger lights to provide a larger illumination pattern used in conjunction with a smaller light to pinpoint a critical area. Larger lights, however, tend to produce more heat and may overload electrical systems.
Efforts to reduce shadow formation have been made. Brendgord et al. U.S. Pat. No. 4,037,096 which issued on July 19, 1977, discloses a single source lighthead used with a multiple reflector optical system. The light rays are directed by means of the multiple reflectors to approach the illuminated area in an angled relationship to the axis of symmetry of the lighting apparatus, rather than parallel to the the axis. Because the light rays approach objects from all angles, they tend to travel around the object, thus, reducing shadow formation on the desired area.
There is a need for a lighting apparatus which offers the shadow reduction features of the single source lighthead and the large field of illumination of the multiple source lighthead. There is a further need for such an apparatus which will also offer intense illumination without sacrificing the size of the field of illumination and without the production of excessive heat. Finally, there is a need, especially in surgical lighting fixtures, for an apparatus which offers a redundant lighting system so that loss of one source will not reduce or eliminate the pattern of illumination.